Salesforce posted their Dreamforce presentations. Below are links to some of the more interesting developer-focused ones. There is no audio.
Sforce and Customforce Hacks – Provides a good look into new functionality being offered in Winter ’06.
AJAX Toolkit – Nothing here you can’t learn from the manual, but is a decent getting started presentation.
Gearing Up – Overview of the PHP, Perl and ForceAmp tools.